The present invention relates to a magnetic bubble memory device, and more particularly to an improvement of a map loop structure suitable for defective-loop handling.
A magnetic bubble memory device usually uses a major/minor loop scheme which employs a major loop for controlling read/write of information and a plurality of minor loops for storing information. In such a major/minor scheme magnetic bubble memory device, one loop (map loop) is provided for the plurality of data storing minor loops (data loops) stored in the map loop are defect information of the respective minor loops, an index code for address synchronization of the magnetic bubble memory device and an error correction code. Accordingly, the map loop requires a larger number of bits than the number of the data storing minor loops.
However, when the number of bits of each minor loop (which is equal to the number of bits of the map loop because the conventional map loop has the same loop configuration as that of the minor loops) is equal to or smaller than the number of minor loops, the defective-loop information cannot be stored in the map loop. In order to increase a memory capacity, the increase of the number of minor loops (corresponding to the number of bits per page) is necessary.